Lighting system for an endoscope

ABSTRACT

A lighting system for an endoscope includes a lamp positioned so that an optical axis thereof is oriented horizontally; a light guide having an incident end upon which the illuminating light from the lamp is incident; a diaphragm plate rotated about a pivot so as to advance into and retract from an optical path of the illuminating light, the pivot extending parallel to the optical axis of the lamp and positioned above or below the optical path. The diaphragm plate includes a notch which is formed at one end of the diaphragm plate, the notch being positioned along an arc which is centered about the pivot and which intersects a center of the light guide when the diaphragm plate rotates about the pivot; and a large number of minute perforations formed along and below the arc.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a lighting system which suppliesilluminating light to an end of a light guide for an endoscope.

[0003] 2. Description of the Related Art

[0004] A xenon lamp, which is known as a high-intensity lamp with a lowheating value, is widely used as a light source for inputtingilluminating light to a light guide of an endoscope. In a state wherethe xenon lamp is fixed so that the axis thereof extends horizontally,the amount of light emitted from the xenon lamp oscillates in an areaabove the axial center of the light emitted from the xenon lamp due tothe phenomenon of oscillation which occurs at convection or electricaldischarge of the xenon gas sealed in the xenon lamp, or due to someother reason.

[0005] A small amount of such oscillations present no problem as long asthe amount of the light having no fluctuations is relatively greaterthan that the amount of light having fluctuations when the degree ofopening of a diaphragm is great. However, the fluctuations of the lightamount show up as flicker in the illuminating light when the degree ofopening of the diaphragm becomes small, and such flicker becomes moreconspicuous as the degree of opening of the diaphragm decreases. Thismay obstruct the observing operation of the endoscope.

[0006] To prevent such a problem from occurring, there has been proposeda diaphragm device disclosed in Japanese Unexamined Patent PublicationNo.2001-340293. In this patent publication, as shown in FIG. 4, a pairof right and left diaphragm plates 91 are disposed to be capable ofintercepting an optical path A of the illuminating light emitted from alamp to the incident end of a light guide from the right and left sidesof the optical path A, respectively. At least one of the pair ofdiaphragm plates 91 is provided with a projecting portion 92 whichintercepts only an upper portion of the optical path A when the degreeof opening of an aperture (i.e., the diaphragm plates 91) of the opticalpath A is extremely small.

[0007] The pair of diaphragm plates 91 are pivoted at a pivot 93positioned straight above the optical path A. In a state where thedegree of opening of an aperture of the optical path A is made extremelysmall by the pair of diaphragm plates 91, only a light bundle which ispassed through a gap between the pair of diaphragm plates 91 which isformed in a vertically-lower half portion of the optical path A isincident on the incident end of a light guide.

[0008] In a conventional lighting device for an endoscope such asdiscussed above, the pair of diaphragm plates 91 must be rotated aboutthe pivot 93 very finely to control the amount of illuminating lightincident on the incident end of the light guide when the degree ofopening of an aperture of the optical path A is extremely small.

[0009] Therefore, when a subject is observed closely through theendoscope, at the time the degree of opening of an aperture of theoptical path A is generally made extremely small, even an extremelyslight positional error or slight play in a drive system for driving thepair of diaphragm plates 91 tends to cause a substantial error in theamount of illuminating light incident on the incident end of the lightguide, which makes the control of that amount of the incident lightinaccurate.

[0010] Providing the drive system with reduction gearing having a highspeed reduction ratio to prevent such a problem increases the number ofelements of the drive system, and therefore increases the productioncost of the drive system. At the same time, the amount of illuminatinglight incident on the incident end of the light guide cannot becontrolled smoothly due to backlash and play occurring in such reductiongearing. As a result of this, a substantial delay (the extent to whichis visually observable) occurs in control of the amount of illuminatinglight incident on the incident end of the light guide.

SUMMARY OF THE INVENTION

[0011] The present invention provides a lighting system for an endoscopewhich does not cause ‘flicker’ in the illuminating light incident on theincident end of a light guide due to the aforementioned phenomenon ofoscillation that occurs at convection or electrical discharge of thexenon gas sealed in the xenon lamp, especially when the degree ofopening of a diaphragm of the lighting system is extremely small, andwhich makes it possible to control the amount of illuminating lightincident on the incident end of the light guide smoothly and preciselywith a simple structure.

[0012] According to an aspect of the present invention, a lightingsystem for an endoscope is provided, including a lamp for supplyingilluminating light, the lamp being positioned so that an optical axisthereof is oriented horizontally; a light guide having an incident endupon which the illuminating light from the lamp is incident; and adiaphragm plate rotated about a pivot so as to advance into and retractfrom an optical path of the illuminating light, the pivot extendingparallel to the optical axis of the lamp and positioned one of above andbelow the optical path. The diaphragm plate includes a notch which isformed at one end of the diaphragm plate, the notch being positionedalong an arc which is centered about the pivot and which intersects acenter of the light guide when the diaphragm plate rotates about thepivot. A large number of minute perforations are formed along and belowthe arc.

[0013] It is desirable for the diameters of the large number of minuteperforations to vary successively in a predetermined direction.

[0014] The large number of minute perforations can be aligned in aplurality of rows along the arc on the diaphragm plate.

[0015] The large number of minute perforations can be formed on thediaphragm plate at positions thereon no more than half of a radius ofthe optical path away from the arc.

[0016] It is desirable for the diameters of the large number of minuteperforations to decrease in a direction away from the notch.

[0017] It is desirable for the diaphragm plate to rotate about the pivotso as to advance into and retract from the optical path in a directionorthogonal to the optical axis of the optical path.

[0018] It is desirable for the diaphragm plate to be fixed at one endthereof to a rotating shaft of a drive motor, the notch being formed atthe other end of the diaphragm plate.

[0019] It is desirable for the pivot to extend parallel to the opticalaxis of the optical path.

[0020] Each perforation of the large number of minute perforations canbe circular in shape.

[0021] It is desirable for the notch to be formed so as to besubstantially symmetrical with respect to the arc, a width of the notchgradually decreasing in a direction along the arc toward an innermostportion of the notch.

[0022] The present disclosure relates to subject matter contained inJapanese Patent Application No.2002-27503 (filed on Feb. 5, 2002) whichis expressly incorporated herein by reference in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be described below in detail withreference to the accompanying drawings in which:

[0024]FIG. 1 is a front elevational view of a diaphragm plate of anembodiment of a lighting system for an endoscope, according to thepresent invention;

[0025]FIG. 2 is a cross sectional view of the lighting system shown inFIG. 1;

[0026]FIG. 3 is a front elevational view of a diaphragm plate of anotherembodiment of a lighting system for an endoscope, according to thepresent invention; and

[0027]FIG. 4 is a front elevational view of a pair of diaphragm platesof a conventional lighting system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028]FIG. 2 shows a state where a light guide connector 1 forconnecting a light guide 3 of an optical fiber endoscope (not shown) toa lighting system 10 is coupled to a connector socket 12 of the lightingsystem 10.

[0029] The lighting system 10 is provided therein with a lamp (lightsource) 11 which includes a xenon light bulb 11 a and a concavereflector 11 b. In the lamp 11, the xenon light bulb 11 a is fixed sothat the axis thereof extends horizontally while the concave reflector11 b is arranged so that the axis thereof is coincident with the axis ofthe xenon light bulb 11 a to make the light reflected by the concavereflector 11 b converge in the vicinity of an incident end 2 of thelight guide 3.

[0030] The incident end 2 of the light guide 3 is positioned on anoptical axis B of an optical path A of illuminating light emitted fromthe lamp 11 toward the incident end 2. The lighting system 10 isprovided with a rotatable diaphragm plate (light intercepting plate) 13.The diaphragm plate 13 is disposed so that it can advance into andretract from the optical path A in a path between the lamp 11 and theincident end 2.

[0031] An upper end portion of the diaphragm plate 13 is fixed directlyto a rotating shaft (pivot/pivotal shaft) 14 a of a drive motor 14 whichis positioned above the optical path A so that the diaphragm plate 13can be driven to rotate about the rotating shaft 14 a. The drive motor14 can be, e.g., a servomotor.

[0032] The rotating shaft 14 a of the drive motor 14 is arrangeddirectly above the optical axis B to extend parallel to the optical axisB. Due to this arrangement, the diaphragm plate 13 can advance into andretract from the optical path A in a direction orthogonal to the opticalaxis B of the optical path A. Therefore, the degree of opening of anaperture of the optical path A depends on the rotational position of thediaphragm plate 13, and accordingly, the amount of illuminating lightincident on the incident end 2 of the light guide 3 depends on therotational position of the diaphragm plate 13.

[0033]FIG. 1 shows a front elevational view of the diaphragm plate 13.The diaphragm plate 13 is formed as a substantially L-shaped plate asshown in FIG. 1, and is provided, at a free bottom end thereof on oneside (right side as viewed in FIG. 1) of the free bottom end, with anotch 13 a for varying the area of an aperture of the optical path Awhich is intercepted by the diaphragm plate 13 in accordance with therotational position of the diaphragm plate 13.

[0034] A one-dot chain line arc C shown in FIG. 1 represents the movingpath of the optical axis B which is generated on the diaphragm plate 13when the diaphragm plate 13 rotates about the rotating shaft 14 arelative to the optical axis B. The notch 13 a is formed to besubstantially symmetrical with respect to the arc C, and is furtherformed so that the width of the notch 13 a gradually decreases in adirection toward the base (innermost portion) of the notch 13 a.

[0035] Due to such a structure, when the degree of opening of anaperture of the optical path A is not extremely small, the area of anaperture of the optical path A which is intercepted by the diaphragmplate 13 varies by varying the position of the notch 13 a with respectto the optical path A, which makes it possible to promptly control theamount of illuminating light incident on the incident end 2 of the lightguide 3.

[0036] When a subject is observed closely through endoscope, the amountof illuminating light incident on the incident end 2 of the light guide3 needs to be controlled finely in a state where the degree of openingof an aperture of the optical path A is extremely small.

[0037] To make such a fine control possible, the diaphragm plate 13 isprovided thereon, along the arc C of the optical axis B of the opticalpath A, with a large number of circular minute perforations 13 b.

[0038] The large number of minute perforations 13 b are aligned in tworows and arranged at regular intervals in each row, and the diameters ofthe large number of minute perforations 13 b decrease in a directionaway from the notch 13 a. With this structure, the area of an apertureof the optical path A which is intercepted by the diaphragm plate 13varies by a variation of the rotational position of the diaphragm plate13 in a state where the degree of opening of an aperture of the opticalpath A is extremely small.

[0039] Accordingly, the area of the aperture of the optical path A canbe changed by a relatively large variation of the rotational position ofthe diaphragm plate 13. As a consequence, the amount of illuminatinglight incident on the incident end 2 of the light guide 3 can be finelycontrolled with the diaphragm plate 13 directly coupled to the rotatingshaft 14 a. Therefore, the amount of illuminating light incident on theincident end 2 of the light guide 3 can be controlled smoothly with nosubstantial delay and without being affected by any backlash or playlike that which may occur if a reduction gear train or a cam mechanismwas provided between the rotating shaft 14 a and the diaphragm plate 13.

[0040] In an alternative embodiment, as shown in FIG. 3, the rotatingshaft 14 a of the drive motor 14 is arranged directly below the opticalaxis B to extend parallel to the optical axis B. Due to thisarrangement, similar to the embodiment shown in FIG. 1, a diaphragmplate 113 can advance into and retract from the optical path A in adirection orthogonal to the optical axis B of the optical path A

[0041] In the illustrated embodiments shown in FIGS. 1 and 3, the largenumber of minute perforations 13 b are formed on the diaphragm plate 13below the arc C at positions no more than half of a radius of theoptical path A away from the arc C. Due to this structure, onlydesirable light bundles in the vicinity of the optical axis B which areconsidered to exhibit a small range of variation in color temperatureare incident on the incident end 2 of the light guide 3.

[0042] In addition, the large number of minute perforations 13 b areformed on the diaphragm plate 13 along the arc C (i.e., a arc of theoptical axis B which is generated on the diaphragm plate 13 when thediaphragm plate 13 is driven to rotate about the rotating shaft 14 a ofthe drive motor 14) at positions only below the arc C.

[0043] Due to this structure, in a state where the degree of opening ofan aperture of the optical path A is extremely small, all the lightbundles emitted from an upper half of the xenon lamp bulb 11 a, thelight amount of which fluctuates, are intercepted by the diaphragm plate13 to thereby prevent flicker from occurring in the illuminating lightincident on the incident end 2 of the light guide 3.

[0044] Although the xenon lamp bulb 11 a is used as a light source ofthe lamp 1 for inputting illuminating light to the light guide 3 in theabove illustrated embodiment, the xenon lamp bulb 11 a can be replacedby a different type of light source.

[0045] Although the large number of minute perforations 13 b are formedon the diaphragm plate 13 at regular intervals in the above illustratedembodiment, a similar effect can be expected even if the large number ofminute perforations 13 b are formed at irregular intervals, and even ifthe minute perforations 13 b are partly formed on the arc C.

[0046] As can be understood from the above description, according to alighting system of an endoscope to which the present invention isapplied, the amount of illuminating light incident on the incidentsurface of the light guide can be controlled by a relatively largerotation of the diaphragm plate since a large number of minuteperforations for varying the area of an aperture of an optical path ofthe illuminating light in accordance with the rotational position of thediaphragm plate, in a state where the degree of opening of an apertureof the optical path of the of the illuminating light is extremely small,are formed on the diaphragm plate along a arc of the optical axis of theoptical path which is generated on the diaphragm plate when thediaphragm plate rotates about a pivot. With this structure, the amountof illuminating light incident on the incident end of the light guidecan be controlled smoothly and precisely with a simple structureespecially when the degree of opening of an aperture of the optical pathA is extremely small. Moreover, only desirable light bundles which donot generate any flicker in the illuminating light incident on theincident end of the light guide can be supplied to the incident end ofthe light guide since the large number of minute perforations are formedon the diaphragm plate 13 at positions thereon only below the arc on thediaphragm plate.

[0047] Obvious changes may be made in the specific embodiment of thepresent invention described herein, such modifications being within thespirit and scope of the invention claimed. It is indicated that allmatter contained herein is illustrative and does not limit the scope ofthe present invention.

What is claimed is:
 1. A lighting system for an endoscope, comprising: alamp for supplying illuminating light, said lamp being positioned sothat an optical axis thereof is oriented horizontally; a light guidehaving an incident end upon which said illuminating light from said lampis incident; and a diaphragm plate rotated about a pivot so as toadvance into and retract from an optical path of said illuminatinglight, said pivot extending parallel to said optical axis of said lampand positioned one of above and below said optical path; wherein saiddiaphragm plate comprises: a notch which is formed at one end of saiddiaphragm plate, said notch being positioned along an arc which iscentered about said pivot and which intersects a center of said lightguide when said diaphragm plate rotates about said pivot, and a largenumber of minute perforations formed along and below said arc.
 2. Thelighting system for an endoscope according to claim 1, wherein diametersof said large number of minute perforations vary successively in apredetermined direction.
 3. The lighting system for an endoscopeaccording to claim 1, wherein said large number of minute perforationsare aligned in a plurality of rows along said arc on said diaphragmplate.
 4. The lighting system for an endoscope according to claim 1,wherein said large number of minute perforations are formed on saiddiaphragm plate at positions thereon no more than half of a radius ofsaid optical path away from said arc.
 5. The lighting system for anendoscope according to claim 2, wherein said diameters of said largenumber of minute perforations decrease in a direction away from saidnotch.
 6. The lighting system for an endoscope according to claim 1,wherein said diaphragm plate rotates about said pivot so as to advanceinto and retract from said optical path in a direction orthogonal tosaid optical axis of said optical path.
 7. The lighting system for anendoscope according to claim 1, wherein said diaphragm plate is fixed atone end thereof to a rotating shaft of a drive motor, said notch beingformed at the other end of said diaphragm plate.
 8. The lighting systemfor an endoscope according to claim 1, wherein said pivot extendsparallel to said optical axis of said optical path.
 9. The lightingsystem for an endoscope according to claim 1, wherein each perforationof said large number of minute perforations is circular in shape. 10.The lighting system for an endoscope according to claim 1, wherein saidnotch is formed to be substantially symmetrical with respect to saidarc, a width of said notch gradually decreasing in a direction alongsaid arc toward an innermost portion of said notch.